Am just getting my head round Twisted, threading, stackless, etc. etc. and would appreciate some high level advice.
Suppose I have remote clients 1 and 2, connected via a websocket running in a page on their browsers. Here is the ideal goal:
for cl in (1,2):
guess[cl] = show(cl, choice("Pick a number:", range(1,11)))
checkpoint()
if guess[1] == guess[2]:
show((1,2), display("You picked the same number!"))
Ignoring the mechanics of show, choice and display, the point is that I want the show call to be asynchronous. Each client gets shown the choice. The code waits at checkpoint() for all the threads (or whatever) to rejoin.
I would be interested in hearing answers even if they involve hairy things like rewriting the source code. I'd also be interested in less hairy answers which involve compromising a bit on the syntax.
In Python, the most widely-used approach to async/event-based network programming that hides that model from the programmer is probably gevent.
Beware: this kind of trickery works by making tasks yield control implicitly, which encourages the same sorts of surprising bugs that tend to appear when OS threads are involved. Local reasoning about such problems is significantly harder than with explicit yielding, and the convenience of avoiding callbacks might not be worth the trouble introduced by the inherent pitfalls. Perhaps just as important to a library author like yourself: this approach is not pure Python, and would force dependencies and interpreter restrictions on the users of your library.
A lot of discussion about this topic sprouted up (especially between the gevent and twisted camps) while Guido was working on the asyncio library, which was called tulip at the time. He summarized the main issues here.